Process for bleaching sand.



- iron in small quantities JOHN GUSTAF ADOLF RHODIN, OF LONDON, ENGLAND.

PROCESS FOR, BLEACHING SAND.

No Drawing.

To all whom it may concern.

Be it known that I, JOHN GUSTAF AnoLF RHoDIN, a subject of the King of Sweden, residing at London, England, have invented certain new and useful Improvements in Processes for Bleaching Sand, of which the following is a specification.

This invention relates to an means for and process of bleaching sand, in which the discoloration is due to metallic salts or oxids. In the majority of cases this discoloration is caused by iron compounds, and this invention relates primarily to the removal of such bodies, although the process is applicable also to the removal of discolorations caused by many other metals.

In effect, the process consists in mixing the material to be bleached with a fixed alkaline chlorid such as for instance, common salt, (sodium chlorid) roasting the mixture, and finally lixiviating. In the case of sand discolored by iron compounds ferric chlorid is produced, a large .part of which is removed by volatilization during the roasting process, the remainder being removed by lixiviation. It follows that the process is applicable to all sands in which the discoloration is caused by substances which at the temperature of the reaction form readily soluble compounds when roasted with common salt, or other suitable fixed alkaline chlorid.

It has already been proposed to remove from sand by first reducing the iron to a metallic state, and then removing the majority of the iron by magnetic means, while the last traces are separated by heating With ammonium chlorid. Common salt has also been used for removing copper from ores containing it'together with sulfur, and this forms no part of my invention, which relates to bleaching sand only, and which differs from previously known processes both in that it is far simpler and more economical to carry out, as well as being considerably more efficient than such previously known process.

The invention is carried out as follows The sand to be treated should be as free as possible from manganese and where the discoloration is due mainly to iron, the sand is mixed with about 23 by weight of common salt (sodium chlorid). The salt may be added in a dry state, or as a brine solution; for the purpose of manufacture it Specification of Letters Patent.

improved I hasbeen completed, the sand appears Patented Feb. 29, 1916.

Application filed March 29, 1915. Serial No. 17,843.

is immaterial whether the method. of mixing is a dry or a wet one; but as it is very much easier to obtain an intimate and uniform mixture by a wet method of mixing,

the wet process using brine solution is preferred. The mass so mixed is then placed in a suitable roasting furnace, which may be of a reverberatory type, or of a muflle or other suitable type. The mixture is then heated to a temperature of 1100 1200 C., for a period of between one and two hours or more, and the furnace is preferably so arranged that the flame is an oxidizing one. After cooling the mass is taken out, and if necessary lixiviated in the well known manner. As ferric chlorid, which isv produced during the roasting process, is very volatile, a large amount of this is removed during the roasting process, and it may not be necessary in all cases to resort to lixiviation. After the process of a brilliant and lustrous white color, and is thus suitable for a variety of purposes for which it was not suitable in itsdiscolored state; for instance, it may now be used with white cement for concrete making and other like purposes.

The mechanism of the reaction taking place is not quite clear, but it seems'probable. that what takes place may be represented by the following equation ss o +re o +euaoizaNa sio',+2Feci,

In some cases a slight rose color is perceptible in sand which has been treated in the manner described above, and it is difiicult to say whether this is due to refraction of light or to traces of manganese, as cases have occurred where this slight color was present, although no manganesecould be found even by the most careful methods of analysis.

If there should be any discoloration due to copper, it will be found that this is removed even more easily than in the case of iron, and that a shorter heat treatment will suilice for the purpose.

' I do not desire to limit the scope of the invention to the precise details of quantities, temperature or duration of heating, which have been given merely as a guidance for carrying out the process, and which can of course be varied within reasonable limits to suit indivldual cases and var in 2:

intensities of discoloration. Further other fixed alkaline chlorids, as for example potassium chlorid may be used in similar proportions.

I claim v.

1. In a process for bleaching discolored sand containing iron, the use of fixedalkali-chlorids for producing and removing soluble compounds from the bodies With Which the sand is discolored.

2. In a process for bleaching discolored sand containing iron, the use of fixedalkali-chlorids for producing and removing volatile compounds from the bodies Wllll'l Which the sand is discolored.

3. In a process for bleaching discolored sand containing iron, the use of fixedalkali-chlorids for producing and removing -mon salt solution, drying and roasting the mixture, cooling the mass and finally lixivi ating the same. a

' In testimony whereof I have afiixed my signature in presence of two wltnesses.

JQHN GUSTAF ADOLF RHODIN.

Witnesses:-

FRANK B. DELIN, F. C. I-IoHs. 

